The present invention pertains to a tool for tightening strap around an object or load and adhering the strap onto itself. More particularly, the present invention is directed to a two-piece strapping tool, comprising a manually-operated tensioner and a battery-operated sealer, that is configured to tension a strap around a load, weld or melt-adhere the strap onto itself and sever the strap from a strap source (e.g., supply).
Strapping tools (or “strappers”) are well-known in the art. These tools come in a wide variety of types, from fully manual tools to automatic, table-top tools. Such tools generally are designed for use with either metal strapping or plastic/polymeric strap.
Strappers for applying plastic or polymeric strapping materials can be of the automatic, table-top type or portable, hand-held type and can be either electrically or pneumatically driven. This is necessary in order to provide energy for tensioning the strapping material and adhering the strap onto itself. Typically, the adhering function is provided by melting or otherwise welding a section of the polymeric (plastic) strapping material onto itself. Such melting or welding operations are generally carried out using ultrasonic or vibrational-type weld assemblies. The movement or vibrational motion can be provided by electrical, electromechanical or fluid drive (hydraulic or pneumatic) systems.
The prior art has developed several types of portable strappers. In one such exemplary prior art strapper, a pneumatic system is used to drive the motors to tension the strap (driving a tensioning wheel), and to move a vibrating element that is in contact with interfacial surfaces of overlapping plastic strap portions. The tool includes a pneumatic circuit to route the compressed gas (air) to the appropriate functional elements (clamps and motors) through valves and the like. In such a tool, the various functional elements are large and as such can be cumbersome. In addition, many such tools use one or more large (and heavy) mechanical clutch(es) to hold or clamp the strap following tension.
Thus, the prior art has developed smaller, more compact and more lightweight hand-held strappers, also known as “combination tools” because such tools combine the functions of tensioning, welding and cutting the strap into a single, one-piece hand-held device. Once such prior art strapper is battery-powered device that incorporates an electromechanical tensioning mechanism along with an electromechanical welding mechanism. In one embodiment, the strapper operates by using battery-powered electric motor to tension the strap around the load in a first stage, then using a second battery-powered electric motor to frictionally weld the strap to itself in a second stage. In another embodiment, a single electric motor may be used to drive both the tensioning and welding stages.
While the design of such one-piece, hand-held, battery-powered strappers is a significant improvement over the prior art, the prior art has not addressed the additional advantages that may achieved by separating the tensioning and welding functions into separate, independent components, with the tensioning component being manually-operated and the welding component being battery-operated. Separating the tensioning and welding functions into two separate components, while seemingly inconsistent with the prior art trend to consolidate strapper functionality into smaller and more compact one-piece devices, provides several significant advantages.
For example, the weight of each of the two individual components is less than the weight of a prior art one-piece strapper tool. Thus, the two-piece system is lighter, less cumbersome and easier to manipulate. Additionally, by making the tensioning function a manual operation, the battery life of the welding component is advantageously extended since no battery power is used in the tensioning operation. Finally, by making the tensioning function a manual operation, a higher strap tension is desirably achievable because the tensioning power of battery-operated strappers is limited by the battery strength and the size and strength of the motor driving the tensioning function.
Accordingly, there exists a need for a hand-held strapping tool that separates the tensioning function and the welding function into independent components. Desirably, the tensioning function is accomplished using a manually-operated tensioner that tensions a strap about a load and maintains the desired strap tension during the welding process. More desirably, the welding function is accomplished using a battery-operated sealer that uses a vibrational-type weld assembly to weld overlapping portions of the strap and a cutting assembly to cut the strap from the supply. Most desirably, the tensioner is configured to matingly receive the sealer, such that the sealer may be positioned between the tensioner support legs in order to readily engage the overlapping portions of the strap.